sleeper1987
New Member
Hi. I'm trying to make an LED cube - an 8x8x8 array of LEDs to be driven by a micro-controller. Problem is, I need to source and sink currents from separate output pins.
- One output needs to source current for 1 to 8 LEDs in parallel.
- Eight outputs need to sink current from each of those LEDs individually.
What I have currently is this system:
(see attached file - led_driver.jpg)
In reality, the base voltages are controlled by the output pins, rather than by the source directly.
I'm unsure as to what's going on with the diode here, as it's between the transistors. In my circuit, the whole array of LEDs goes off for seconds at a time, or flickers, and I gather this may be due to the sink diodes oscillating due to their having slightly different gains. Can anyone offer some advice as to how to make this work?
NB: The diodes will only be on for a 1/64 duty cycle, so I'm happy to overdrive them with 80-100 mA of current. Also, I'm aware that 1/64 will be a crappy brightness, but I want to get the basic thing working, then I'll switch to using SIPO registers to controls the 64 columns independently.
Thanks in advance!
- One output needs to source current for 1 to 8 LEDs in parallel.
- Eight outputs need to sink current from each of those LEDs individually.
What I have currently is this system:
(see attached file - led_driver.jpg)
In reality, the base voltages are controlled by the output pins, rather than by the source directly.
I'm unsure as to what's going on with the diode here, as it's between the transistors. In my circuit, the whole array of LEDs goes off for seconds at a time, or flickers, and I gather this may be due to the sink diodes oscillating due to their having slightly different gains. Can anyone offer some advice as to how to make this work?
NB: The diodes will only be on for a 1/64 duty cycle, so I'm happy to overdrive them with 80-100 mA of current. Also, I'm aware that 1/64 will be a crappy brightness, but I want to get the basic thing working, then I'll switch to using SIPO registers to controls the 64 columns independently.
Thanks in advance!